Circadian · Metabolic health
Circadian misalignment and your health
The human circadian system coordinates physiology across virtually every organ — from glucose and lipid metabolism to immune function, blood pressure, and hormonal secretion. When sleep-wake timing is chronically misaligned with the internal body clock, the consequences extend well beyond feeling tired.
What circadian misalignment does to the body
Experimental studies inducing circadian misalignment demonstrate impaired glucose tolerance, elevated blood pressure and heart rate, elevated inflammatory cytokines, reduced vaccine response, and suppression of anabolic hormones including testosterone and growth hormone. These effects are distinct from sleep deprivation and can persist even when total sleep duration is adequate (Scheer FAJL et al., PNAS 2009; Roenneberg T et al., Curr Biol 2012). Shift workers and those with severe delayed sleep-wake phase disorder are particularly affected.
Treatable circadian conditions
Delayed sleep-wake phase disorder (DSWPD) — the clinical form of the colloquially described "night owl" phenotype — is common and significantly undertreated. Patients are often told they simply need to go to bed earlier, without acknowledgment that their circadian timing is physiologically anchored hours later than the conventional schedule. Effective treatment exists: timed bright light therapy in the morning, evening light restriction, low-dose melatonin, and chronotherapy when appropriate can meaningfully advance the clock.
Non-24-hour sleep-wake rhythm disorder, irregular sleep-wake rhythm disorder, and shift-work disorder each have distinct clinical features and management approaches.
Key references
- Roenneberg T et al. Social jetlag and obesity. Curr Biol 2012;22(10):939–943.
- Scheer FAJL et al. Adverse metabolic and cardiovascular consequences of circadian misalignment. PNAS 2009;106(11):4453–4458.
- Foster RG et al. Sleep and circadian rhythm disruption in social jetlag and mental illness. Ann N Y Acad Sci 2013;1264(1):110–118.
- Dibner C, Schibler U. Metabolic timing. Annu Rev Physiol 2015;77:23–54.
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